Process contribution evaluation for COD removal and energy production from molasses wastewater in a BioH2–BioCH4–MFC-integrated system

Abstract

In this study, a three-stage-integrated process using the hydrogenic process (BioH), methanogenic process (BioCH), and a microbial fuel cell (MFC) was operated using molasses wastewater. The contribution of individual processes to chemical oxygen demand (COD) removal and energy production was evaluated. The three-stage integration system was operated at molasses of 20 g-COD L, and each process achieved hydrogen production rate of 1.1 ± 0.24 L-H L day, methane production rate of 311 ± 18.94 mL-CH L day, and production rate per electrode surface area of 10.8 ± 1.4 g m day. The three-stage integration system generated energy production of 32.32 kJ g-COD and achieved COD removal of 98 %. The contribution of BioH, BioCH, and the MFC reactor was 20.8, 72.2, and, 7.0 % of the total COD removal, and 18.7, 81.2, and 0.16 % of the total energy production, respectively. The continuous stirred-tank reactor BioH at HRT of 1 day, up-flow anaerobic sludge blanket BioCH at HRT of 2 days, and MFC reactor at HRT of 3 days were decided in 1:2:3 ratios of working volume under hydraulic retention time consideration. This integration system can be applied to various configurations depending on target wastewater inputs, and it is expected to enhance energy recovery and reduce environmental impact of the final effluent.

Critical Review on Two-Stage Anaerobic Digestion with H2 and CH4 Production from Various Wastes

“…Integrated approaches using a two-stage AD process with other technologies, such as microbial fuel cells (MFCs), photo fermentation (PF), etc., have attracted much attention due to more diversified products and better elimination of organic wastes [81,82].…”

“…Research on MFCs in integrating systems has focused on their potential for the simultaneous degradation of residual organics and electricity energy recovery [82,83]. A coupling system of a two-stage AD process and subsequent MFC achieved higher energy conversion efficiency and overall COD removal (60.0% and 94.1%, respectively) from water hyacinth, compared to the two-stage AD (19.0% and 81.5%, respectively) [84].…”